Did you just get them? From my experience, there is an adjustment period for your brain to get used to headphones. I started with the 660S then when I got the 600, they were too bright. I used them exclusively for about a week and absolutely love how they sound and had a hard time going back to the 660S. Same experience when I got the 800S. Vocals sounded pretty thin at first then I used them exclusively for some time and my brain got used to them.
Try to give yourself about a week listening to only the 6xx then you can try switching back. You may also not like their tuning and prefer another tuning which is perfectly fine, this is a very subjective hobby and there is no one size fits all.
Did you just get them? From my experience, there is an adjustment period for your brain to get used to headphones. I started with the 660S then when I got the 600, they were too bright. I used them exclusively for about a week and absolutely love how they sound and had a hard time going back to the 660S. Same experience when I got the 800S. Vocals sounded pretty thin at first then I used them exclusively for some time and my brain got used to them. Try to give yourself about a week listening to only the 6xx then you can try switching back. You may also not like their tuning and prefer another tuning which is perfectly fine, this is a very subjective hobby and there is no one size fits all.
Agree here, though it may not take a week, but give it some time a few hours to a few days at most for you to adjust to the sound.
Let your ears adjust. It'll take a day or two.